The main objective of the study proposed is the preparation and characterization of Fv fragment from mouse myeloma proteins with antibody activity, from human myeloma proteins and from conventionally induced antibodies. This fragment contains only the variable portions of the heavy and light chains and it is half the size of Fab. The approach for its preparation will be by mild enzymic digestion of the inter-domain area. It is intended to determine the molecular weights, N-terminal and C-terminal sequences of Fv and its peptide chains, as well as the binding properties of Fv, and to study the interaction between the peptide chains (V sub L and V sub H) which comprise Fv. Further investigation of the structure-function relationship in the antibody site, by chemical modification and affinity labeling will be carried out. Experiments will be conducted for the preparation of crystals from Fv fragments derived from myeloma proteins with antibody activity, which will be suitable for X-ray analysis. Fv fragments and their peptide chains will be utilized for the preparation of antisera to various subgroups of V sub L and V sub H and these antisera will be used for the study of cell-receptors in particular on T-cells. The possibility to obtain Fv fragment, based on our experience with protein 315, provide a unique opportunity for fine-structure analysis of antibody combining site.